(1) Field of the Invention
The present invention relates generally to stator winding bars and, more particularly, to an apparatus and method for repairing electrical generator stator leaks, cracks and crevices as may be generally classified in United States Patent and Trademark Office Classification 29/596.
(2) Description of the Prior Art
Certain electrical devices, for example, power generators, have water cooled stator bars. The stator windings comprise insulated copper bars that are assembled in slots and brazed into copper clips on the ends to form bar assemblies. Each stator bar includes a combination of solid and hollow copper conductors, referred to as strands. The hollow strands provide a means for circulating coolant through the strand package to prevent the machine from overheating and to increase the output of the generator by removing heat from the insulated stator bars. The copper clips themselves form water boxes on either end of the stator bars and have coolant water openings or connections formed therethrough.
Leaks within stator bars are caused by corrosion of the brazed joints and/or porosity in the clip casting. Prior art methods for repairing leaking stator bars involve varying degrees of generator disassembly to fix individual clips, or in some cases, complete removal and replacement of the stator bars. Either option requires considerable downtime to gain access to the stator bars, which makes these repairs costly and time consuming.
U.S. Pat. No. 5,557,837 to Thiard-Laforet et al. discloses a method for repairing stator winding bars. In the disclosed method, the existing connecting device is removed from the bar end by inductive heating. The bar end is cleaned in the region where the new connecting device is intended to be mounted. The end surface of the bar end is material cutting machined. Narrow slots are introduced between adjacent conductor elements into the end of the bar in the transverse and vertical directions. A first connecting part which is made of copper and completely surrounds the bar end is pushed on. Remaining gaps between the first connecting part and the outer surfaces of the bar end are filled with copper foil and/or solder foil. The narrow slots are filled with copper foil and/or solder foil or a combination of both. The first connecting part and the bar end are inductively heated and soldered with the addition of solder. The solder joint thus created is inspected and a second connecting part is fitted to the free end surface of the first connecting part by soldering. The sealing of the resulting connecting device is tested.
U.S. Pat. No. 4,776,082 to Janzer discloses an electric motor repair. The method includes drilling holes through the armature at various locations around the armature and along its length. The holes extend to the armature shaft. Adhesive is injected into the holes, under pressure, and fills any voids between the laminations and between the armature and the shaft.
U.S. Pat. No. 4,614,226 to Ryan discloses a vehicle heater repair apparatus and method. The apparatus has a closed loop pipe system removably connected to vehicle heater input and output lines which have been disconnected from the engine under the vehicle hood. The water inlet is connected to a water source for allowing the injection of water into the pipe system. A valve allows the water to be shut on or off. A pump is connected to the pipe system. Sealant solution and cleaning solution tanks are connected to the piping system for first injecting a cleaning solution for circulation through the vehicle heater core and later for circulating a sealing solution. An electrical heater is also connected to the pipe system for heating the liquids. The pipe system has a drain connection through a valve and through a pressure relief valve for dumping the water and the cleaning solution and the sealant solution after the cleaning and sealing has been completed. The cleaning solution tank and the sealing solution tank are connected to a source of air for applying the solutions under pressure into the piping system.
Thus, there remains a need for a new and improved apparatus and method for repairing leaks, cracks, and crevices in water cooled stator bars of electrical generators which does not require partial or complete disassembly of the stator bars or clips while, at the same time, does not adversely affect the performance of the generator.